What was found
AIRCRAFT WAS GROUNDED: DURING APPROACH WITH ENGINES AT REDUCED OR IDLE POWER, DIRTY SOCK SMELL THROUGHOUT CABIN. LESS NOTICEABLE AT HIGHER POWER SETTINGS. ALSO NOTICED THE SAME SMELL AT THE GATE WHEN OPERATING ON APU BLEED. MAINTENANCE FOUND THE APU AIR / OIL VENT LINE HAD EVIDENCE OF COKING AND REPLACED THE VENT LINE. A DECONTAMINATION OF THE ENVIRONMENTAL CONTROL SYSTEM WAS ACCOMPLISHED PER TASK CARD 26L00021014. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED WITH NO ODORS NOTED.